function collapse(obj, menu) {
    if (document.getElementById(menu).style.display == "") {
        obj.style.cssText = "background-image:url(../images/ad_title_bg_hide.gif)"; 
        document.getElementById(menu).style.display = "none";
    }
    else {
        obj.style.cssText = "background-image:url(../images/ad_title_bg_show.gif)";
        document.getElementById(menu).style.display = "";
    }
}